1. Field of the Invention
This invention relates to a marking apparatus and more particularly to a marking apparatus having a plurality of wheels rotatably positioned on a shaft and including a plurality of marking characters on the periphery of each wheel such that the marking characters are selectively moved into marking position.
2. Description of the Prior Art
U.S. Pat. Nos. 3,541,954 and 3,654,860 disclose devices for impressing upon billets, slabs, and the like a group of marking characters by marking wheels having a plurality of characters on the outer periphery of the wheels. Character selection is accomplished by rotating each marking wheel until the desired character on the wheel periphery is in marking position. Each wheel has a ratchet portion on one side that is actuated by a pawl connected to an actuating slide. The pawl rotates the marking wheel for character selection. A position indicator associated with the marking wheel transmits a signal to a remote location for indicating the relative position of the marking wheel. With this arrangement the relative angular position of each marking wheel and the character in marking position is indicated remotely. A spiral cam is provided on each rotatable wheel, and a signal device in abutting relation with the spiral cam transmits a signal to the remote location to thereby indicate the relative angular position of the wheel.
Number printing and recording devices for selectively marking sheets of material with letters and/or numbers are known in the art and include wheels or rolls having marking characters positioned on the periphery thereof. The wheels or rolls are selectively rotated to position the desired character in marking position. Examples of such devices are disclosed in the following U.S. Pat. Nos. 2,891,469; 2,909,992; 2,923,233; 3,598,044; 3,603,251; 3,616,749; 3,859,914 and 3,938,436.
One problem encountered with character selection of a marking wheel is wear of the pawl that is engageable with the ratchet portion of the wheel by the continued application of force upon the pawl to rotate the pawl and thereby turn the wheel to move the next adjacent character into marking position. With the conventionally known devices, after the pawl has been moved into engagement with the ratchet portion, the pawl is swung in an arcuate path through a preselected angle by the application of a force directly upon the pawl. This direct application of force to the pawl to swing the pawl and thereby turn the wheel after a period of continued use necessitates a replacement of the pawl and other associated components, such as the return spring which normally maintains the pawl disengaged from the wheel.
Therefore, there is need to provide in a marking apparatus, having a marking wheel selectively engaged by a pawl, means for moving the pawl to rotate the wheel without directly applying force to the pawl so as to eliminate wear thereon and extend the life of the pawl and increase the efficiency of the marking apparatus.